The annihilation of dark matter can lead to observable signatures in high-energy gamma rays across the Milky Way sky. I will review the current status of such dark matter searches with data from the Fermi Large Area Telescope. The centers of galaxies, dense in dark matter, provide the best targets to search for annihilation signatures. I will begin with the center of our own Galaxy, where an observed gamma-ray excess had been interpreted as a signal of dark matter. Using a novel data analysis method, however, we showed that the excess is more consistent with a population of unresolved astrophysical sources, such as millisecond pulsars. These new sources may be fossil remnants from Galactic bulge formation, possibly providing a window into the formation history of the Milky Way. Then, I will discuss searches in galaxies outside our own, including the Milky Way dwarfs as well as thousands of other galaxies outside the Local Group. We have built a catalog of the most promising dark matter targets out to redshifts of ~0.03. Using this catalog, we have obtained the best sensitivity on extragalactic dark matter annihilation to date, with results complementing existing dwarf studies. This catalog is widely applicable to annihilation or decay signatures into neutral cosmic-rays, regardless of wavelength, messenger, or instrument.